Selling Spanish Cars in Spain

Has anyone sold a Spanish car privately in Spain and if so is it difficult to complete the paperwork (ie change of registration, change of insurance)

We are looking at buying a new car offering our Seat Cordoba (year 2000) as part exchange and can only get an offer of 2500 Euros from Main Dealers, we paid 6500 Euros two and a half years ago, so would hope to get 4000 euros now.